Treatment of metal



Patented Oct. 13, .1942

2,298,280 I TREATMENT or METAL Wilfred James Clifford and Henry HewardAdams,

Brentford, England, assignors to Parker Rust- Proof Company, Detroit ofMichigan No Drawing.

Original a 1939, Serial No. 254,238.

, Mich., a corporation pplication February 2,

Divided and this a'pplication March 21, 1941, Serial No. 384,541. InGreat Britain February 4, 1938 Claims.

This invention relates to the treatment of metals, especially iron orsteel, for instance to the treatment of metals with phosphate coatingsolutions in order to improve the resistance of the meals to corrosionor to provide a corrosion-resisting base for paints.

It is an object of the invention to accelerate the action of reagentswhich attack a metal surface.

It is a further object of the invention to accelerate the action ofphosphate coating solutions, i. e., to reduce the time taken by thecoating solution to form a complete coating,- or to reduce thetemperature, or to obtain a better coating in a given time under givenconditions than if the compounds were not present.

Where phosphate and similar coating solutions are being employed, theymay be applied to the metal in any suitable manner, for instance byspraying, brushing, flowing or immersion methods.

We have found that the action of' reagents which attack metal surfaces,and especially phosphate coating solutions, can be accelerated byincorporating hydroxylamine therein.

The cleaned steel sheet in the examples given below is a steel sheet inits original bright rolled condition rendered substantially free fromgrease by wiping with clean white spirit.

While the hydroxylamine may be the only accelerator' present in acoating bath, it may also be employed in conjunction with otheraccelerators, for instance metallic accelerators such as coppercompounds or oxidizing agents such as nitrates or nitrites. The presenceof'copper ions appears to promote heavier and darker coatings, and thepresence of a nitrate such as zinc nitrate appears to give a slightfurther acceleration.

The optimum concentration of the accelerating compound in the reagentattacking the metal surfaces differs with different compounds but in thecase of phosphate coating solutions is in general from about .0l% to.4%by weight of the solution. Too much or too little of the acceleratingcompound may be detrimental to good results.

The invention is illustrated by the followinir examples:

Example 1 A cleaned steel sheet can be successfully coated by treatingit with an N/5 solution of zinc dihydrogen phosphate (determined byphenol-- phthalein) containing 0.4% of hydroxylamine, at a temperatureof C. 2

Example 2 A cleaned steel sheet can be successfully coated by treatingit at a temperature of 15 to 80 C. with an N/5 solution of manganesedihydrogen phosphate (determined by phenol-phthalein) containing 0.4% ofhydroxylamine.

If in any of the above examples 0.001% of copper (calculated as themetal) is added to the solution, for instance. in the form of thenitrate or carbonate, a darker and slightly heavier coating is obtained,and the addition of zinc nitrat results in a slightly furtheracceleration.

What we claim is: 1

1. A coating solution containing a coating acid phosphate andhydroxylamine in an amount that accelerates the coating action of thesolution.

2. A coating solution containing zinc coating acid phosphate andhydroxylamine in an amount that accelerates the coating action of thesolution.

3. The process which comprises treating ferrous surfaces with aphosphate coating solution, the action of which is accelerated byhydroxylamine until a corrosion-resistant paintholding coating isobtained.

4. A process which comprises treating ferrous surfaces with a zincphosphate coating solution accelerated by hydroxylamine until acorrosionresistant paint-holding coating is obtained.

5. The process which comprises dissolving in a solution materialscomprisin hydroxylamine and the ingredients of a coating acid phosphatein amounts resulting in an accelerated phosphate coating bath, andtreating a ferrous surface with the solution until a phosphate coatingis formed upon said surface.

' WILFRED JAMES CLIFFORD.

HENRY. HEWARD ADAMS.

